Scholarly article on topic 'The natural and artificial radionuclides in drinking water samples and consequent population doses'

The natural and artificial radionuclides in drinking water samples and consequent population doses Academic research paper on "Earth and related environmental sciences"

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Abstract of research paper on Earth and related environmental sciences, author of scientific article — Aydan Altıkulaç, Şeref Turhan, Hasan Gümüş

Abstract Concentration levels of 226Ra, 228Ra, 40K and 137Cs were determined in 52 drinking water samples collected from the different supplies in Samsun province to evaluate annual effective dose due to the ingestion of the drinking water samples. The activity concentrations of 226Ra, 228Ra and 40K natural radionuclides in the drinking water samples varied from <27 to 2431 mBq L−1, <36 to 270 mBq L−1 and <47 to 2880 mBq L−1 respectively. The activity concentrations of the artificial radionuclide 137Cs in the drinking water samples were lower than minimum detectable activity except in one drinking water sample (DW14) with an associated activity concentration of 2576 mBq L−1. Contributions of the consumed water samples to annual effective dose from 226Ra, 228Ra and 40K varied from 1.6 to 33.4 μSv y−1 with a mean of 6.1 μSv y−1, 2.2 to 46.8 μSv y−1 with a mean of 8.6 μSv y−1, 4.7 to 97.5 μSv y−1 with a mean of 17.9 μSv y−1 for infants, children and adults, respectively. The results showed that all values of the annual effective dose of ingestion of these water samples were below the individual dose criterion of 100 μSv y−1 reported by World Health Organization (WHO).

Academic research paper on topic "The natural and artificial radionuclides in drinking water samples and consequent population doses"

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The natural and artificial radionuclides in drinking water samples and consequent population doses

qi Aydan Altikulag a, §eref Turhan b'*, Hasan Gumus a

a Department of Physics, Faculty of Science, Ondokuz Mayis University, Kurupelit, Samsun, Turkey b Department of Physics, Faculty of Science and Letters, Kastamonu University, 37150 Kastamonu, Turkey

ARTICLE INFO

ABSTRACT

Article history: Received 22 April 2015 Received in revised form 4 June 2015 Accepted 24 June 2015 Available online xxx

Keywords: Drinking water Natural radioactivity Annual effective dose

0K 37Cs

Concentration levels of 226Ra, 228Ra, 40K and 137Cs were determined in 52 drinking water samples collected from the different supplies in Samsun province to evaluate annual effective dose due to the ingestion of the drinking water samples. The activity concentrations of 226Ra, 228Ra and 40K natural radionuclides in the drinking water samples varied from <27 to 2431 mBq L-1, <36 to 270 mBq and <47 to 2880 mBq respectively. The activity concentrations of the artificial radionuclide 137Cs in the drinking water samples were lower than minimum detectable activity except in one drinking water sample (DW14) with an associated activity concentration of 2576 mBq L_1. Contributions of the consumed water samples to annual effective dose from 226Ra, 228Ra and 40K varied from 1.6 to

33.4 mSv y 1 with a mean of 6.1 mSv y-1, 2.2 to 46.8 mSv y_1 with a mean of 8.6 mSv y-1, 4.7 to

97.5 mSv y_1 with a mean of 17.9 mSv y_1 for infants, children and adults, respectively. The results showed that all values of the annual effective dose of ingestion of these water samples were below the individual dose criterion of 100 mSv y_1 reported by World Health Organization (WHO).

Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Drinking water contains naturally occurring radionuclides such as such as uranium-radium (238U-226Ra) and thorium (232Th) decay series, their decay products and potassium (40K) and artificial radionuclides (137Cs, 134Cs, 90Sr, etc.) coming from the fallout from atmospheric nuclear weapons testing and the accidents at nuclear reactors. In consequence of radioactive fallout after the Chernobyl nuclear reactor accident in 1986, 137Cs radionuclide (T1/2 = 30.07 y) was widely dispersed in the Turkish environment (Turhan et al., 2012). These radionuclides could present a risk to human health

(WHO, 2011). Low doses caused by ingestion of these radionuclides in drinking water can increase the radiological risk of longer term effects.

Radium isotopes (226Ra and 228Ra) are the most radiotoxic and dangerous element in case of ingestion due to their similarity in behaviour to calcium, an element commonly fixed in bones (Martin Sanchez, Rubio Montero, Gomez Escobar, & Jurado Vargas, 1999). The 226Ra (T1/2 = 1600 y) and 228Ra (T1/ 2 = 5.75 y) can dissolve easily in water and travel within the aquifer. The most common source of them in drinking water is from radiological decay of naturally occurring 238U and 232Th found in the earth's crust (Landsberger & George, 2013). 40K is present as a very small fraction of naturally occurring

* Corresponding author. Tel.: +90 366 280 19 40; fax: +90 366 215 49 69. E-mail address: serefturhan@ymail.com (S. Turhan).

Peer review under responsibility of The Egyptian Society of Radiation Sciences and Applications. http://dx.doi.org/10.1016/j.jrras.2015.06.007

1687-8507/Copyright © 2015, The Egyptian Society of Radiation Sciences and Applications. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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potassium (39K), which is an element found in the earth's crust, oceans, and all organic material. Once taken in, 40K behaves in the body in the same manner as other potassium isotopes. Humans require potassium to sustain biological processes, with most (including 40K) being almost completely absorbed upon ingestion, moving quickly from the gastro intestinal tract to the bloodstream. The 40K that enters the bloodstream after ingestion or inhalation is quickly distributed to all organs and tissues. It can present both an external and an internal health hazard. The health hazard of 40K is associated with cell damage caused by the ionizing radiation that results from radioactive decay, with the general potential for subsequent cancer induction (ANL, 2005). Caesium (137Cs) reacts with water producing a water-soluble compound. After drinking 137Cs contaminated water, it gets more or less uniformly distributed throughout the body, with the highest concentrations in soft tissue, where it would expose living tissue to gamma and beta radiation. Therefore, determining of the concentration levels of the natural and artificial radionuclides in drinking water is an important factor for public health studies, which allow the assessment of population exposure to radiation by the consumption of water.

Recently, studies relate to the determination of the natural radioactivity in drinking water from different sources were performed worldwide (Agbalagba, Avwiri, & Ononugbo, 2013; Al-Amir, Al-Hamarneh, Al-Abed, & Awadallah, 2012; Beyermann, Bunger, Schmidt, & Obrikat, 2010; Desideri, Roselli, Feduzi, & Meli, 2007; Gorur & Camgoz, 2014; Islam Salih, Pet-tersson, & Lund, 2002; Jankovic, Todorovic, Todorovic, & Nikolov, 2012; Jia, Torri, & Magro, 2009; Kehagia et al., 2007; Landsberger & George, 2013; Osman Alfatih et al., 2008; Rozmaric, Rogic, Benedik, & Strok, 2012; Turhan, Ozcitak, Taskin, & Varinlioglu, 2013; Vesterbacka, 2007; Yalcin et al., 2012). However concentration levels of 226Ra, 228Ra, 40K and 137Cs in drinking water used in Samsun city and its counties and the radiological impacts of the consumed of drinking water have not been reported in literature previously.

Samsun is the biggest city of the Black sea Region and it has the highest tourism potential with road, air, sea and rail transport facilities. Samsun is a long city which extends along the coast between two river deltas (Yesilirmak and Kizilirmak) which jut into the Black Sea. According to the 2013 census, population of Samsun city is 1,261,810. Also the area of the study is so close to the nuclear power facility which is going to be built in Turkey soon. In this study, the activity levels of

Fig. 1 - The location of sampling sites.

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226Ra, 228Ra, 40K and 137Cs in the drinking water samples collected from Samsun city and its counties were determined to evaluate the radiological hazards caused by the consumption of these water samples and ascertain possible changes in environmental radioactivity caused by nuclear, industrial and other human activities.

Material and methods

The activity concentration (A) of radionuclides mentioned above was calculated from the following equation:

A (Bq L"1) = -

Sample collection

The drinking water (surface water) samples were collected from 52 different sampling stations found in the boundaries of Ondokuzmayis, Bafra, Alacam, Yakakent, Kavak, Ladik, Havza, Vezirkoprii, Carsamba, Terme, Ayvacik, Tekkekoy, Salipazari and Asarcik which are counties of Samsun province in the Black Sea region of Turkey (Fig. 1). Geological formations seen in the study area contain sandstone, marl, tuff, basalt and agglomerates, grey-blue marls, clay, siltstone, pebblestone, gypsum, andesite-basalt type volcanic, small amounts of limestone, gravel and silt (Akinci, Dogan, Kilifoglu, & Temiz, 2011). The drinking water samples were collected in 2.5 L polypropylene bottles. Then, the drinking water samples were acidified with nitric acid to avoid the collection of organic materials. All water samples were evaporated in a furnace to reduce their volume to approximately 0.5 L. Each water sample was then filled into cylindrical plastic containers, weighed and hermetically sealed. The water samples were stored for more than 4 weeks before counting so as to allow 224Ra and 226Ra to reach the secular equilibrium with their short-lived decay products.

2.2. Experimental setup

All measurements were performed in the Laboratory of Nuclear Physics of Faculty of Science of Samsun Ondokuz Mayis University. The activity concentrations of 226Ra, 228Ra, 40K and 137Cs in the drinking water samples were measured using a high-resolution gamma ray spectrometer. The spectrometer was consisted of a coaxial p-type HPGe detector (GX3020) with an relative efficiency of 30% relative to a 7.62 cm (diam.) x 7.62 cm cylindrical NaI(Tl) detector. The detector bias voltage was 4000 V and the energy resolution was 0.8 keV at 122 keV and 1.8 keV at 1.33 MeV. For gamma-ray shielding, a front opening split-top shield was used to reduce the background. It features 100 mm lead thickness, which is jacketed by a 9.5-mm steel outer housing. The graded liner comprises 1-mm-thick tin layer and 1.5-mm-thick copper layer to prevent interference by lead X-rays. To minimize scattered radiation from the shield, the detector was centred in it.

Radioactivity analysis

The water sample containers were placed on top of the detector for radioactivity analysis. Measurement time for each sample was sufficiently long to provide good counting statistics. The absolute efficiency calibration of the gamma spec-trometry systems was carried out using the reference materials RG-set (RGU-1, RGTh-1 and RGK-1).

where CN is the net peak area at gamma-ray at energy, et is the efficiency of the detector, Pg is emission probability of

Table 1 - The activity concentrations of natural and artificial radionuclides measured in the drinking water samples.

Sample code

Activity concentration (mBq L 1)

226Ra 228Ra 40K 137Cs

DW1 <32 <38 238 ± 18 <15

DW2 <29 <38 <37 <18

DW3 <28 <28 286 ± 17 <13

DW4 46 ± 6 <37 <67 <19

DW5 <26 <44 <15 <16

DW6 227 ± 11 104 ± 5 <14 <9

DW7 304 ± 14 154 ± 7 <18 <11

DW8 406 ± 16 151 ± 8 <78 <11

DW9 439 ± 15 127 ± 6 394 ± 21 <16

DW10 <22 <22 <57 <10

DW11 296 ± 13 238 ± 10 2311 ± 226 <16

DW12 304 ± 10 228 ± 11 2586 ± 217 <15

DW13 2431 ± 110 99 ± 6 228 ± 20 2576 ± 217

DW14 228 ± 12 182 ± 9 2880 ± 220 <15

DW15 171 ± 10 <36 2531 ± 164 <11

DW16 204 ± 9 <34 1532 ± 146 <11

DW17 250 ± 11 <48 2578 ± 222 <11

DW18 335 ± 14 200 ± 11 2690 ± 220 <13

DW19 229 ± 12 270 ± 11 2659 ± 212 <13

DW20 <31 <26 284 ± 25 <15

DW21 <29 <38 284 ± 24 <18

DW22 <26 <34 177 ± 18 <18

DW23 <30 83 ± 5 189 ± 20 <18

DW24 <23 <33 <25 <17

DW25 <26 <35 <29 <19

DW26 <18 <32 141 ± 16 <20

DW27 <31 88 ± 6 <34 <18

DW28 <20 <33 <43 <20

DW29 <28 <29 182 ± 17 <18

DW30 <31 <38 <66 <18

DW31 <24 <36 158 ± 16 <18

DW32 <23 <34 <44 <17

DW33 <27 <36 264 ± 21 <20

DW34 <27 <37 <68 <12

DW35 <29 <38 320 ± 21 <12

DW36 <37 91 ± 5 <41 <16

DW37 <29 <48 <79 <20

DW38 <23 <47 <88 <18

DW39 <32 <35 <35 <19

DW40 <30 <37 294 ± 30 <20

DW41 <30 <37 267 ± 22 <16

DW42 <29 <43 <49 <20

DW43 <35 64 ± 5 <16 <13

DW44 <20 54 ± 6 <87 <12

DW45 <27 <31 118 ± 12 <20

DW46 <18 <37 223 ± 21 <22

DW47 <32 <38 159 ± 17 <20

DW48 <23 <35 216 ± 21 <18

DW49 <40 <51 271 ± 29 <21

DW50 <29 <38 181 ± 17 <20

DW51 <30 <40 200 ± 14 <16

DW52 <26 <28 142 ± 11 <14

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g-Pg'tc-V

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Table 2 - Comparison of the activity concentrations of natural radionuclides with those reported for other country.

Country Activity concentration of the natural Reference

radionuclide (mBq L"1)

226Ra 228Ra 40K

Italy 9 5 - Jia et al., 2009

USA (Texas) 150 42 - Landsberger & George, 2013

Nigeria (Niger Delta) 8900 8100 39,800 Agbalagba et al., 2013

Spain 2 <85 - UNSCEAR, 2008

Russian Fed. 7 13 UNSCEAR, 2008

Turkey (Samsun) 419 142 806 This study

radionuclide of interest, tc is the total counting time (s) and V is the sample volume (L). The gamma-ray peak of the 351.9 keV from 214Pb and the 911.2 keV from 228Ac were used to determine the activity concentration of 226Ra and 228Ra, respectively. The activity concentration of 40K and 137Cs was measured directly by their own gamma-ray line at 1460.8 keV and 661.7 keV, respectively. Minimum detectable activity (MDA) of the gamma-ray measurements was calculated by the equation (Currie, 1968):

MDA (Bq L"1) = -

, • Y -, • I • \

where LLD is the lower limit of detection, as defined below (Currie, 1968)

LLD = 2.71 + 4.65\/B (3)

where B is the number of counts for the background spectrum.

The MDAs of 226Ra, 228Ra, 40K and 137Cs calculated for each

sample varied from 18 to 40 mBq with a mean of 27 mBq L_1, 22 to 51 mBq L^1 with a mean of 36 mBq L_1,14 to 88 mBq L^1 with a mean of 47 mBq L^1 and 9 to 22 mBq L^1 with a mean of 16 mBq L_1, respectively.

Results and discussion

The activity concentrations of the radionuclides

The activity concentrations of 226Ra, 228Ra, 40K and 1 measured in the drinking water samples are given in Table 1. The activity concentrations of 226Ra, 228Ra and 40K varied from <27 to 2431 mBq L_1, <36 to 270 mBq L^1 and <47 to 2880 mBq L^1 respectively. It can be seen from Table 1 that the activity concentrations of 226Ra measured in 38 water samples (73% of the total water samples) are below the MDA value. The mean activity concentration of 226Ra measured in 14 water samples is 419 mBq L_1. The activity concentrations of 228Ra measured in 37 water samples (71% of the total water samples) are below the MDA value. The mean activity concentration of 228Ra measured in 15 water samples is 142 mBq L_1. The activity concentrations of 40K measured in 21 water samples (40% of the total water samples) are below the MDA value. The mean activity concentration of 40K measured in 31 water samples is 806 mBq L_1. Ayvacik County (DW13 and DW14) appears to have the highest concentrations of 226Ra and 40K, whereas Kavak County exhibits the highest concentration of 228Ra. The activity concentrations of 137Cs in the water samples were lower than the MDA values

with the exception of one drinking water sample (DW14, 2576 mBq L_1) contamination of 137Cs due to the Chernobyl nuclear accident. The measured activity concentrations of the natural radionuclides were compared with the data reported worldwide in Table 2. The activity concentrations of 226Ra, 228Ra and 40K are well below the WHO guidance levels of 1000,100 and 10,000 mBq L_1, respectively.

3.2. Inhalation exposure through ingestion of drinking water

The ingestion of the radionuclides depends on the consumption rates of food and water and on radionuclide concentrations (UNSCEAR, 2008). Annual effective dose (AEDdw) due to the ingestion of the drinking water samples was estimated to evaluate the radiological hazards members of the public (infant, children and adult). The AEDdw (mSv y_1) was estimated using the activity concentrations of the radionuclides, dose coefficients and annual water consumption as follows:

AEDdw = A x DCF x CRw

where A is the activity concentration of the radionuclides (226Ra, 228Ra, 40K and 137Cs) (mBq L"1), DCF is the dose conversion factors (2.8 x 10"4, 6.9 x 10"4, 6.2 x 10"6 and 1.3 x 10"5 mSv Bq"1 for 226Ra, 228Ra, 40K and 137Cs, respectively) (ICRP, 1996) and CRw is the consumption rate of drinking water (250, 350 and 730 L y"1 for infants, children and adults, respectively) (WHO, 2011). The total annual effective doses from the 226Ra, 228Ra and 40K varied from 1.6 to 33.4 mSv y"1 with a mean of 6.1 mSv y"1, 2.2 to 46.8 mSv y"1 with a mean of 8.6 mSv y"1, 4.7 to 97.5 mSv y"1 with a mean of 17.9 mSv y"1 for infants, children and adults, respectively. Contribution of the 137Cs to the annual effective dose is insignificant and has been neglected.

4. Conclusion

The activity concentrations of 226Ra, 228Ra, 40K and 137Cs in the drinking water samples collected from the 52 different water sources in Samsun city were measured to check the compliance with national and international regulation and obtain the data which can be used as a baseline for ascertaining possible changes in environmental radioactivity due to nuclear, industrial and other human activities. This is the first detailed study of the natural and artificial radionuclides concentrations in the drinking water ground samples in Samsun

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city The activity concentrations of the radionuclides measured in the study are lower than guidance levels recommended by WHO. The results showed that the annual effective dose of ingestion of these drinking water samples are lower than the recommended value of 1000 mSv y_1 as reported by WHO.

Acknowledgements

This study was carried out within the framework of a doctoral thesis conducted at University of Ondokuz Mayis University.

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